Munich: Bayern chairman Karl-Heinz Rummenigge stated confidently during the close season that Pep Guardiola, after winning the domestic double in his debut campaign as coach, would never be pushed out.

"Bayern will never sack Pep Guardiola. I can put that in writing today," said Rummenigge of the former Barcelona coach, whose contract at the Allianz Arena runs through to 2016.

However, Guardiola, despite his almost impeccable track record, is aware that there is little margin for error at Germany's biggest club.

He won the Bundesliga, the German Cup, the UEFA Super Cup and the Club World Cup in his first season in Bavaria but his team's defence of the Champions League ended in a semifinal humbling at the hands of Real Madrid.

"There are no secrets. If I don't win, then probably another coach comes here next year," he stated.

Bayern are expected to win the domestic double for a third year running, but even then Guardiola knows that his team will probably have to win the Champions League for 2014-15 to be deemed a successful season, especially with the final being played in Berlin.

But his team's preparations for the defence of their Bundesliga crown, starting at home to Wolfsburg on Friday, have hardly been ideal.

The summer has seen Bayern sell Toni Kroos to Real Madrid after negotiations over a new deal stalled, with the club unwilling to bow to the midfielder's wage demands. Croatian striker Mario Mandzukic has gone to Atletico Madrid while veteran Belgian defender Daniel Van Buyten has retired.

Uncertainties The signing of last season's Bundesliga top scorer Robert Lewandowski from biggest rivals Borussia Dortmund represents an upgrade in attack, but it is unclear what the other new signings will offer.

Defensive midfielder Sebastian Rode, signed from Eintracht Frankfurt, is likely only to be a squad player, while it remains to be seen where young Spanish left-back Juan Bernat — described as "extraordinary" by sporting director Matthias Sammer — will play in a Bayern side that could line up with a three-man defence.

The other new recruit is Pepe Reina, who arrives from Liverpool to provide back-up in goal for Manuel Neuer.

Guardiola continues to experiment with different systems and could be tempted to deploy both Philipp Lahm and David Alaba in midfield in front of three central defenders.

However, he has lost one defender, Javi Martinez, until the end of the year after the Spaniard suffered a knee injury in the SuperCup defeat to Borussia Dortmund last week.

Now, the coach is hoping to bring in a new face in defence, although he admitted that: "If it's not possible, so be it. We will just keep working with the players we already have."

One of those is Holger Badstuber, who played his first competitive game after more than 20 months out injured in last weekend's German Cup first-round win at Preussen Munster.

"I'm ready and I'm feeling great. Every training session and match does me the world of good," said the 25-year-old.

In midfield, Thiago Alcantara is not expected to return from a knee injury until October while Bastian Schweinsteiger will miss the opening weeks of the season.

What Guardiola would love is for Mario Goetze, the scorer of Germany's winning goal in the World Cup final, to produce his top form regularly after flattering to deceive last season.

But Goetze and the other seven Bayern first-team regulars who were involved until the final weekend of the World Cup will need time to build up their fitness, and the opening weeks will be vital.

"I can see Bayern having a few difficulties to start with until they get all of their World Cup winners properly fit and integrated back into the side," former Bayern and Dortmund coach Ottmar Hitzfeld told bundesliga.com.

Bayern, who have always been heavily represented in the Germany squad, have failed to win the title in either of the last two seasons following a World Cup and their rivals will now be hoping for another slip-up.